chromium/chrome/test/data/extensions/platform_apps/isolation/set_cookie.html

<html>
<body>
<script>
  // Tomorrow.
  var expire = new Date(Date.now() + 24 * 60 * 60 * 1000);
  document.cookie = 'testCookie=1; path=/; expires=' + expire + ';'
</script>
</body>
</html>